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Revision 1.26 by root, Sun Aug 7 03:34:07 2005 UTC vs.
Revision 1.115 by root, Mon Sep 24 18:14:00 2007 UTC

…		…
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# Event	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
		23
		24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
		32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		34
		35	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	37	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
24		39
25	# Glib/Gtk2	40	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
28		43
29	# Tk	44	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
32		47
33	# Danga::Socket	48	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
36		51
37
38	=head1 DESCRIPTION	52	=head1 DESCRIPTION
39		53
40	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
41	operating system supports.	55	operating system supports.
42		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for
		68	example sockets), using these functions on file descriptors that
		69	support nonblocking operation (again, sockets, pipes etc.) is very
		70	inefficient. Use an event loop for that (such as the L<Event|Event>
		71	module): IO::AIO will naturally fit into such an event loop itself.
		72
43	Currently, a number of threads are started that execute your read/writes	73	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	74	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	75	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	76	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	77	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	78	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	79	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	80	aio_write, so the remaining functionality would have to be implemented
		81	using threads anyway.
51		82
52	Although the module will work with in the presence of other threads, it is	83	Although the module will work in the presence of other (Perl-) threads,
53	currently not reentrant, so use appropriate locking yourself, always call	84	it is currently not reentrant in any way, so use appropriate locking
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	85	yourself, always call C<poll_cb> from within the same thread, or never
55	C<aio_> functions) recursively.	86	call C<poll_cb> (or other C<aio_> functions) recursively.
		87
		88	=head2 EXAMPLE
		89
		90	This is a simple example that uses the Event module and loads
		91	F</etc/passwd> asynchronously:
		92
		93	use Fcntl;
		94	use Event;
		95	use IO::AIO;
		96
		97	# register the IO::AIO callback with Event
		98	Event->io (fd => IO::AIO::poll_fileno,
		99	poll => 'r',
		100	cb => \&IO::AIO::poll_cb);
		101
		102	# queue the request to open /etc/passwd
		103	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		104	my $fh = shift
		105	or die "error while opening: $!";
		106
		107	# stat'ing filehandles is generally non-blocking
		108	my $size = -s $fh;
		109
		110	# queue a request to read the file
		111	my $contents;
		112	aio_read $fh, 0, $size, $contents, 0, sub {
		113	$_[0] == $size
		114	or die "short read: $!";
		115
		116	close $fh;
		117
		118	# file contents now in $contents
		119	print $contents;
		120
		121	# exit event loop and program
		122	Event::unloop;
		123	};
		124	};
		125
		126	# possibly queue up other requests, or open GUI windows,
		127	# check for sockets etc. etc.
		128
		129	# process events as long as there are some:
		130	Event::loop;
		131
		132	=head1 REQUEST ANATOMY AND LIFETIME
		133
		134	Every C<aio_*> function creates a request. which is a C data structure not
		135	directly visible to Perl.
		136
		137	If called in non-void context, every request function returns a Perl
		138	object representing the request. In void context, nothing is returned,
		139	which saves a bit of memory.
		140
		141	The perl object is a fairly standard ref-to-hash object. The hash contents
		142	are not used by IO::AIO so you are free to store anything you like in it.
		143
		144	During their existance, aio requests travel through the following states,
		145	in order:
		146
		147	=over 4
		148
		149	=item ready
		150
		151	Immediately after a request is created it is put into the ready state,
		152	waiting for a thread to execute it.
		153
		154	=item execute
		155
		156	A thread has accepted the request for processing and is currently
		157	executing it (e.g. blocking in read).
		158
		159	=item pending
		160
		161	The request has been executed and is waiting for result processing.
		162
		163	While request submission and execution is fully asynchronous, result
		164	processing is not and relies on the perl interpreter calling C<poll_cb>
		165	(or another function with the same effect).
		166
		167	=item result
		168
		169	The request results are processed synchronously by C<poll_cb>.
		170
		171	The C<poll_cb> function will process all outstanding aio requests by
		172	calling their callbacks, freeing memory associated with them and managing
		173	any groups they are contained in.
		174
		175	=item done
		176
		177	Request has reached the end of its lifetime and holds no resources anymore
		178	(except possibly for the Perl object, but its connection to the actual
		179	aio request is severed and calling its methods will either do nothing or
		180	result in a runtime error).
		181
		182	=back
56		183
57	=cut	184	=cut
58		185
59	package IO::AIO;	186	package IO::AIO;
60		187
61	no warnings;	188	no warnings;
		189	use strict 'vars';
62		190
63	use base 'Exporter';	191	use base 'Exporter';
64		192
65	use Fcntl ();
66
67	BEGIN {	193	BEGIN {
68	$VERSION = 1.1;	194	our $VERSION = '2.41';
69		195
70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	196	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	aio_fsync aio_fdatasync aio_readahead);	197	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	198	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
		199	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
		200	aio_chown aio_chmod aio_utime aio_truncate);
		201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		203	min_parallel max_parallel max_idle
		204	nreqs nready npending nthreads
		205	max_poll_time max_poll_reqs);
		206
		207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
73		208
74	require XSLoader;	209	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	210	XSLoader::load ("IO::AIO", $VERSION);
76	}	211	}
77		212
78	=head1 FUNCTIONS	213	=head1 FUNCTIONS
79		214
80	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
81		216
82	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
83	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
84	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
85	which must be a code reference. This code reference will get called with	220	which must be a code reference. This code reference will get called with
…		…
88	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
89		224
90	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	226	internally until the request has finished.
92		227
		228	All functions return request objects of type L<IO::AIO::REQ> that allow
		229	further manipulation of those requests while they are in-flight.
		230
93	The filenames you pass to these routines I<must> be absolute. The reason	231	The pathnames you pass to these routines I<must> be absolute and
94	for this is that at the time the request is being executed, the current	232	encoded as octets. The reason for the former is that at the time the
95	working directory could have changed. Alternatively, you can make sure	233	request is being executed, the current working directory could have
96	that you never change the current working directory.	234	changed. Alternatively, you can make sure that you never change the
		235	current working directory anywhere in the program and then use relative
		236	paths.
		237
		238	To encode pathnames as octets, either make sure you either: a) always pass
		239	in filenames you got from outside (command line, readdir etc.) without
		240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		241	your pathnames to the locale (or other) encoding in effect in the user
		242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		243	use something else to ensure your scalar has the correct contents.
		244
		245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		246	handles correctly wether it is set or not.
97		247
98	=over 4	248	=over 4
99		249
		250	=item $prev_pri = aioreq_pri [$pri]
		251
		252	Returns the priority value that would be used for the next request and, if
		253	C<$pri> is given, sets the priority for the next aio request.
		254
		255	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		256	and C<4>, respectively. Requests with higher priority will be serviced
		257	first.
		258
		259	The priority will be reset to C<0> after each call to one of the C<aio_*>
		260	functions.
		261
		262	Example: open a file with low priority, then read something from it with
		263	higher priority so the read request is serviced before other low priority
		264	open requests (potentially spamming the cache):
		265
		266	aioreq_pri -3;
		267	aio_open ..., sub {
		268	return unless $_[0];
		269
		270	aioreq_pri -2;
		271	aio_read $_[0], ..., sub {
		272	...
		273	};
		274	};
		275
		276
		277	=item aioreq_nice $pri_adjust
		278
		279	Similar to C<aioreq_pri>, but subtracts the given value from the current
		280	priority, so the effect is cumulative.
		281
		282
100	=item aio_open $pathname, $flags, $mode, $callback	283	=item aio_open $pathname, $flags, $mode, $callback->($fh)
101		284
102	Asynchronously open or create a file and call the callback with a newly	285	Asynchronously open or create a file and call the callback with a newly
103	created filehandle for the file.	286	created filehandle for the file.
104		287
105	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	288	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
109	list. They are the same as used by C<sysopen>.	292	list. They are the same as used by C<sysopen>.
110		293
111	Likewise, C<$mode> specifies the mode of the newly created file, if it	294	Likewise, C<$mode> specifies the mode of the newly created file, if it
112	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	295	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
113	except that it is mandatory (i.e. use C<0> if you don't create new files,	296	except that it is mandatory (i.e. use C<0> if you don't create new files,
114	and C<0666> or C<0777> if you do).	297	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		298	by the umask in effect then the request is being executed, so better never
		299	change the umask.
115		300
116	Example:	301	Example:
117		302
118	aio_open "/etc/passwd", O_RDONLY, 0, sub {	303	aio_open "/etc/passwd", O_RDONLY, 0, sub {
119	if ($_[0]) {	304	if ($_[0]) {
…		…
122	} else {	307	} else {
123	die "open failed: $!\n";	308	die "open failed: $!\n";
124	}	309	}
125	};	310	};
126		311
		312
127	=item aio_close $fh, $callback	313	=item aio_close $fh, $callback->($status)
128		314
129	Asynchronously close a file and call the callback with the result	315	Asynchronously close a file and call the callback with the result
130	code. I<WARNING:> although accepted, you should not pass in a perl	316	code. I<WARNING:> although accepted, you should not pass in a perl
131	filehandle here, as perl will likely close the file descriptor another	317	filehandle here, as perl will likely close the file descriptor another
132	time when the filehandle is destroyed. Normally, you can safely call perls	318	time when the filehandle is destroyed. Normally, you can safely call perls
133	C<close> or just let filehandles go out of scope.	319	C<close> or just let filehandles go out of scope.
134		320
135	This is supposed to be a bug in the API, so that might change. It's	321	This is supposed to be a bug in the API, so that might change. It's
136	therefore best to avoid this function.	322	therefore best to avoid this function.
137		323
		324
138	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	325	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
139		326
140	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	327	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
141		328
142	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	329	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
143	into the scalar given by C<data> and offset C<dataoffset> and calls the	330	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
144	callback without the actual number of bytes read (or -1 on error, just	331	callback without the actual number of bytes read (or -1 on error, just
145	like the syscall).	332	like the syscall).
		333
		334	If C<$offset> is undefined, then the current file descriptor offset will
		335	be used (and updated), otherwise the file descriptor offset will not be
		336	changed by these calls.
		337
		338	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		339
		340	If C<$dataoffset> is less than zero, it will be counted from the end of
		341	C<$data>.
		342
		343	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		344	is outstanding. Modifying it can result in segfaults or World War III (if
		345	the necessary/optional hardware is installed).
146		346
147	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	347	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
148	offset C<0> within the scalar:	348	offset C<0> within the scalar:
149		349
150	aio_read $fh, 7, 15, $buffer, 0, sub {	350	aio_read $fh, 7, 15, $buffer, 0, sub {
151	$_[0] > 0 or die "read error: $!";	351	$_[0] > 0 or die "read error: $!";
152	print "read $_[0] bytes: <$buffer>\n";	352	print "read $_[0] bytes: <$buffer>\n";
153	};	353	};
154		354
		355
		356	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		357
		358	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		359	reading at byte offset C<$in_offset>, and starts writing at the current
		360	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		361	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		362	other.
		363
		364	This call tries to make use of a native C<sendfile> syscall to provide
		365	zero-copy operation. For this to work, C<$out_fh> should refer to a
		366	socket, and C<$in_fh> should refer to mmap'able file.
		367
		368	If the native sendfile call fails or is not implemented, it will be
		369	emulated, so you can call C<aio_sendfile> on any type of filehandle
		370	regardless of the limitations of the operating system.
		371
		372	Please note, however, that C<aio_sendfile> can read more bytes from
		373	C<$in_fh> than are written, and there is no way to find out how many
		374	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		375	provides the number of bytes written to C<$out_fh>. Only if the result
		376	value equals C<$length> one can assume that C<$length> bytes have been
		377	read.
		378
		379
155	=item aio_readahead $fh,$offset,$length, $callback	380	=item aio_readahead $fh,$offset,$length, $callback->($retval)
156		381
157	C<aio_readahead> populates the page cache with data from a file so that	382	C<aio_readahead> populates the page cache with data from a file so that
158	subsequent reads from that file will not block on disk I/O. The C<$offset>	383	subsequent reads from that file will not block on disk I/O. The C<$offset>
159	argument specifies the starting point from which data is to be read and	384	argument specifies the starting point from which data is to be read and
160	C<$length> specifies the number of bytes to be read. I/O is performed in	385	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
164	file. The current file offset of the file is left unchanged.	389	file. The current file offset of the file is left unchanged.
165		390
166	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	391	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
167	emulated by simply reading the data, which would have a similar effect.	392	emulated by simply reading the data, which would have a similar effect.
168		393
		394
169	=item aio_stat $fh_or_path, $callback	395	=item aio_stat $fh_or_path, $callback->($status)
170		396
171	=item aio_lstat $fh, $callback	397	=item aio_lstat $fh, $callback->($status)
172		398
173	Works like perl's C<stat> or C<lstat> in void context. The callback will	399	Works like perl's C<stat> or C<lstat> in void context. The callback will
174	be called after the stat and the results will be available using C<stat _>	400	be called after the stat and the results will be available using C<stat _>
175	or C<-s _> etc...	401	or C<-s _> etc...
176		402
…		…
186	aio_stat "/etc/passwd", sub {	412	aio_stat "/etc/passwd", sub {
187	$_[0] and die "stat failed: $!";	413	$_[0] and die "stat failed: $!";
188	print "size is ", -s _, "\n";	414	print "size is ", -s _, "\n";
189	};	415	};
190		416
		417
		418	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		419
		420	Works like perl's C<utime> function (including the special case of $atime
		421	and $mtime being undef). Fractional times are supported if the underlying
		422	syscalls support them.
		423
		424	When called with a pathname, uses utimes(2) if available, otherwise
		425	utime(2). If called on a file descriptor, uses futimes(2) if available,
		426	otherwise returns ENOSYS, so this is not portable.
		427
		428	Examples:
		429
		430	# set atime and mtime to current time (basically touch(1)):
		431	aio_utime "path", undef, undef;
		432	# set atime to current time and mtime to beginning of the epoch:
		433	aio_utime "path", time, undef; # undef==0
		434
		435
		436	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		437
		438	Works like perl's C<chown> function, except that C<undef> for either $uid
		439	or $gid is being interpreted as "do not change" (but -1 can also be used).
		440
		441	Examples:
		442
		443	# same as "chown root path" in the shell:
		444	aio_chown "path", 0, -1;
		445	# same as above:
		446	aio_chown "path", 0, undef;
		447
		448
		449	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		450
		451	Works like truncate(2) or ftruncate(2).
		452
		453
		454	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		455
		456	Works like perl's C<chmod> function.
		457
		458
191	=item aio_unlink $pathname, $callback	459	=item aio_unlink $pathname, $callback->($status)
192		460
193	Asynchronously unlink (delete) a file and call the callback with the	461	Asynchronously unlink (delete) a file and call the callback with the
194	result code.	462	result code.
195		463
		464
		465	=item aio_mknod $path, $mode, $dev, $callback->($status)
		466
		467	[EXPERIMENTAL]
		468
		469	Asynchronously create a device node (or fifo). See mknod(2).
		470
		471	The only (POSIX-) portable way of calling this function is:
		472
		473	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		474
		475
		476	=item aio_link $srcpath, $dstpath, $callback->($status)
		477
		478	Asynchronously create a new link to the existing object at C<$srcpath> at
		479	the path C<$dstpath> and call the callback with the result code.
		480
		481
		482	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		483
		484	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		485	the path C<$dstpath> and call the callback with the result code.
		486
		487
		488	=item aio_readlink $path, $callback->($link)
		489
		490	Asynchronously read the symlink specified by C<$path> and pass it to
		491	the callback. If an error occurs, nothing or undef gets passed to the
		492	callback.
		493
		494
		495	=item aio_rename $srcpath, $dstpath, $callback->($status)
		496
		497	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		498	rename(2) and call the callback with the result code.
		499
		500
		501	=item aio_mkdir $pathname, $mode, $callback->($status)
		502
		503	Asynchronously mkdir (create) a directory and call the callback with
		504	the result code. C<$mode> will be modified by the umask at the time the
		505	request is executed, so do not change your umask.
		506
		507
		508	=item aio_rmdir $pathname, $callback->($status)
		509
		510	Asynchronously rmdir (delete) a directory and call the callback with the
		511	result code.
		512
		513
		514	=item aio_readdir $pathname, $callback->($entries)
		515
		516	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		517	directory (i.e. opendir + readdir + closedir). The entries will not be
		518	sorted, and will B<NOT> include the C<.> and C<..> entries.
		519
		520	The callback a single argument which is either C<undef> or an array-ref
		521	with the filenames.
		522
		523
		524	=item aio_load $path, $data, $callback->($status)
		525
		526	This is a composite request that tries to fully load the given file into
		527	memory. Status is the same as with aio_read.
		528
		529	=cut
		530
		531	sub aio_load($$;$) {
		532	aio_block {
		533	my ($path, undef, $cb) = @_;
		534	my $data = \$_[1];
		535
		536	my $pri = aioreq_pri;
		537	my $grp = aio_group $cb;
		538
		539	aioreq_pri $pri;
		540	add $grp aio_open $path, O_RDONLY, 0, sub {
		541	my $fh = shift
		542	or return $grp->result (-1);
		543
		544	aioreq_pri $pri;
		545	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		546	$grp->result ($_[0]);
		547	};
		548	};
		549
		550	$grp
		551	}
		552	}
		553
		554	=item aio_copy $srcpath, $dstpath, $callback->($status)
		555
		556	Try to copy the I<file> (directories not supported as either source or
		557	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		558	the C<0> (error) or C<-1> ok.
		559
		560	This is a composite request that it creates the destination file with
		561	mode 0200 and copies the contents of the source file into it using
		562	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		563	uid/gid, in that order.
		564
		565	If an error occurs, the partial destination file will be unlinked, if
		566	possible, except when setting atime, mtime, access mode and uid/gid, where
		567	errors are being ignored.
		568
		569	=cut
		570
		571	sub aio_copy($$;$) {
		572	aio_block {
		573	my ($src, $dst, $cb) = @_;
		574
		575	my $pri = aioreq_pri;
		576	my $grp = aio_group $cb;
		577
		578	aioreq_pri $pri;
		579	add $grp aio_open $src, O_RDONLY, 0, sub {
		580	if (my $src_fh = $_[0]) {
		581	my @stat = stat $src_fh;
		582
		583	aioreq_pri $pri;
		584	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		585	if (my $dst_fh = $_[0]) {
		586	aioreq_pri $pri;
		587	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		588	if ($_[0] == $stat[7]) {
		589	$grp->result (0);
		590	close $src_fh;
		591
		592	# those should not normally block. should. should.
		593	utime $stat[8], $stat[9], $dst;
		594	chmod $stat[2] & 07777, $dst_fh;
		595	chown $stat[4], $stat[5], $dst_fh;
		596	close $dst_fh;
		597	} else {
		598	$grp->result (-1);
		599	close $src_fh;
		600	close $dst_fh;
		601
		602	aioreq $pri;
		603	add $grp aio_unlink $dst;
		604	}
		605	};
		606	} else {
		607	$grp->result (-1);
		608	}
		609	},
		610
		611	} else {
		612	$grp->result (-1);
		613	}
		614	};
		615
		616	$grp
		617	}
		618	}
		619
		620	=item aio_move $srcpath, $dstpath, $callback->($status)
		621
		622	Try to move the I<file> (directories not supported as either source or
		623	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		624	the C<0> (error) or C<-1> ok.
		625
		626	This is a composite request that tries to rename(2) the file first. If
		627	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		628	that is successful, unlinking the C<$srcpath>.
		629
		630	=cut
		631
		632	sub aio_move($$;$) {
		633	aio_block {
		634	my ($src, $dst, $cb) = @_;
		635
		636	my $pri = aioreq_pri;
		637	my $grp = aio_group $cb;
		638
		639	aioreq_pri $pri;
		640	add $grp aio_rename $src, $dst, sub {
		641	if ($_[0] && $! == EXDEV) {
		642	aioreq_pri $pri;
		643	add $grp aio_copy $src, $dst, sub {
		644	$grp->result ($_[0]);
		645
		646	if (!$_[0]) {
		647	aioreq_pri $pri;
		648	add $grp aio_unlink $src;
		649	}
		650	};
		651	} else {
		652	$grp->result ($_[0]);
		653	}
		654	};
		655
		656	$grp
		657	}
		658	}
		659
		660	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		661
		662	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		663	efficiently separate the entries of directory C<$path> into two sets of
		664	names, directories you can recurse into (directories), and ones you cannot
		665	recurse into (everything else, including symlinks to directories).
		666
		667	C<aio_scandir> is a composite request that creates of many sub requests_
		668	C<$maxreq> specifies the maximum number of outstanding aio requests that
		669	this function generates. If it is C<< <= 0 >>, then a suitable default
		670	will be chosen (currently 4).
		671
		672	On error, the callback is called without arguments, otherwise it receives
		673	two array-refs with path-relative entry names.
		674
		675	Example:
		676
		677	aio_scandir $dir, 0, sub {
		678	my ($dirs, $nondirs) = @_;
		679	print "real directories: @$dirs\n";
		680	print "everything else: @$nondirs\n";
		681	};
		682
		683	Implementation notes.
		684
		685	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		686
		687	After reading the directory, the modification time, size etc. of the
		688	directory before and after the readdir is checked, and if they match (and
		689	isn't the current time), the link count will be used to decide how many
		690	entries are directories (if >= 2). Otherwise, no knowledge of the number
		691	of subdirectories will be assumed.
		692
		693	Then entries will be sorted into likely directories (everything without
		694	a non-initial dot currently) and likely non-directories (everything
		695	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		696	likely directories first. If that succeeds, it assumes that the entry
		697	is a directory or a symlink to directory (which will be checked
		698	seperately). This is often faster than stat'ing the entry itself because
		699	filesystems might detect the type of the entry without reading the inode
		700	data (e.g. ext2fs filetype feature).
		701
		702	If the known number of directories (link count - 2) has been reached, the
		703	rest of the entries is assumed to be non-directories.
		704
		705	This only works with certainty on POSIX (= UNIX) filesystems, which
		706	fortunately are the vast majority of filesystems around.
		707
		708	It will also likely work on non-POSIX filesystems with reduced efficiency
		709	as those tend to return 0 or 1 as link counts, which disables the
		710	directory counting heuristic.
		711
		712	=cut
		713
		714	sub aio_scandir($$;$) {
		715	aio_block {
		716	my ($path, $maxreq, $cb) = @_;
		717
		718	my $pri = aioreq_pri;
		719
		720	my $grp = aio_group $cb;
		721
		722	$maxreq = 4 if $maxreq <= 0;
		723
		724	# stat once
		725	aioreq_pri $pri;
		726	add $grp aio_stat $path, sub {
		727	return $grp->result () if $_[0];
		728	my $now = time;
		729	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		730
		731	# read the directory entries
		732	aioreq_pri $pri;
		733	add $grp aio_readdir $path, sub {
		734	my $entries = shift
		735	or return $grp->result ();
		736
		737	# stat the dir another time
		738	aioreq_pri $pri;
		739	add $grp aio_stat $path, sub {
		740	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		741
		742	my $ndirs;
		743
		744	# take the slow route if anything looks fishy
		745	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		746	$ndirs = -1;
		747	} else {
		748	# if nlink == 2, we are finished
		749	# on non-posix-fs's, we rely on nlink < 2
		750	$ndirs = (stat _)[3] - 2
		751	or return $grp->result ([], $entries);
		752	}
		753
		754	# sort into likely dirs and likely nondirs
		755	# dirs == files without ".", short entries first
		756	$entries = [map $_->[0],
		757	sort { $b->[1] cmp $a->[1] }
		758	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		759	@$entries];
		760
		761	my (@dirs, @nondirs);
		762
		763	my $statgrp = add $grp aio_group sub {
		764	$grp->result (\@dirs, \@nondirs);
		765	};
		766
		767	limit $statgrp $maxreq;
		768	feed $statgrp sub {
		769	return unless @$entries;
		770	my $entry = pop @$entries;
		771
		772	aioreq_pri $pri;
		773	add $statgrp aio_stat "$path/$entry/.", sub {
		774	if ($_[0] < 0) {
		775	push @nondirs, $entry;
		776	} else {
		777	# need to check for real directory
		778	aioreq_pri $pri;
		779	add $statgrp aio_lstat "$path/$entry", sub {
		780	if (-d _) {
		781	push @dirs, $entry;
		782
		783	unless (--$ndirs) {
		784	push @nondirs, @$entries;
		785	feed $statgrp;
		786	}
		787	} else {
		788	push @nondirs, $entry;
		789	}
		790	}
		791	}
		792	};
		793	};
		794	};
		795	};
		796	};
		797
		798	$grp
		799	}
		800	}
		801
		802	=item aio_rmtree $path, $callback->($status)
		803
		804	Delete a directory tree starting (and including) C<$path>, return the
		805	status of the final C<rmdir> only. This is a composite request that
		806	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		807	everything else.
		808
		809	=cut
		810
		811	sub aio_rmtree;
		812	sub aio_rmtree($;$) {
		813	aio_block {
		814	my ($path, $cb) = @_;
		815
		816	my $pri = aioreq_pri;
		817	my $grp = aio_group $cb;
		818
		819	aioreq_pri $pri;
		820	add $grp aio_scandir $path, 0, sub {
		821	my ($dirs, $nondirs) = @_;
		822
		823	my $dirgrp = aio_group sub {
		824	add $grp aio_rmdir $path, sub {
		825	$grp->result ($_[0]);
		826	};
		827	};
		828
		829	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		830	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		831
		832	add $grp $dirgrp;
		833	};
		834
		835	$grp
		836	}
		837	}
		838
196	=item aio_fsync $fh, $callback	839	=item aio_fsync $fh, $callback->($status)
197		840
198	Asynchronously call fsync on the given filehandle and call the callback	841	Asynchronously call fsync on the given filehandle and call the callback
199	with the fsync result code.	842	with the fsync result code.
200		843
201	=item aio_fdatasync $fh, $callback	844	=item aio_fdatasync $fh, $callback->($status)
202		845
203	Asynchronously call fdatasync on the given filehandle and call the	846	Asynchronously call fdatasync on the given filehandle and call the
204	callback with the fdatasync result code.	847	callback with the fdatasync result code.
205		848
206	If this call isn't available because your OS lacks it or it couldn't be	849	If this call isn't available because your OS lacks it or it couldn't be
207	detected, it will be emulated by calling C<fsync> instead.	850	detected, it will be emulated by calling C<fsync> instead.
208		851
		852	=item aio_group $callback->(...)
		853
		854	This is a very special aio request: Instead of doing something, it is a
		855	container for other aio requests, which is useful if you want to bundle
		856	many requests into a single, composite, request with a definite callback
		857	and the ability to cancel the whole request with its subrequests.
		858
		859	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		860	for more info.
		861
		862	Example:
		863
		864	my $grp = aio_group sub {
		865	print "all stats done\n";
		866	};
		867
		868	add $grp
		869	(aio_stat ...),
		870	(aio_stat ...),
		871	...;
		872
		873	=item aio_nop $callback->()
		874
		875	This is a special request - it does nothing in itself and is only used for
		876	side effects, such as when you want to add a dummy request to a group so
		877	that finishing the requests in the group depends on executing the given
		878	code.
		879
		880	While this request does nothing, it still goes through the execution
		881	phase and still requires a worker thread. Thus, the callback will not
		882	be executed immediately but only after other requests in the queue have
		883	entered their execution phase. This can be used to measure request
		884	latency.
		885
		886	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		887
		888	Mainly used for debugging and benchmarking, this aio request puts one of
		889	the request workers to sleep for the given time.
		890
		891	While it is theoretically handy to have simple I/O scheduling requests
		892	like sleep and file handle readable/writable, the overhead this creates is
		893	immense (it blocks a thread for a long time) so do not use this function
		894	except to put your application under artificial I/O pressure.
		895
209	=back	896	=back
210		897
		898	=head2 IO::AIO::REQ CLASS
		899
		900	All non-aggregate C<aio_*> functions return an object of this class when
		901	called in non-void context.
		902
		903	=over 4
		904
		905	=item cancel $req
		906
		907	Cancels the request, if possible. Has the effect of skipping execution
		908	when entering the B<execute> state and skipping calling the callback when
		909	entering the the B<result> state, but will leave the request otherwise
		910	untouched. That means that requests that currently execute will not be
		911	stopped and resources held by the request will not be freed prematurely.
		912
		913	=item cb $req $callback->(...)
		914
		915	Replace (or simply set) the callback registered to the request.
		916
		917	=back
		918
		919	=head2 IO::AIO::GRP CLASS
		920
		921	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		922	objects of this class, too.
		923
		924	A IO::AIO::GRP object is a special request that can contain multiple other
		925	aio requests.
		926
		927	You create one by calling the C<aio_group> constructing function with a
		928	callback that will be called when all contained requests have entered the
		929	C<done> state:
		930
		931	my $grp = aio_group sub {
		932	print "all requests are done\n";
		933	};
		934
		935	You add requests by calling the C<add> method with one or more
		936	C<IO::AIO::REQ> objects:
		937
		938	$grp->add (aio_unlink "...");
		939
		940	add $grp aio_stat "...", sub {
		941	$_[0] or return $grp->result ("error");
		942
		943	# add another request dynamically, if first succeeded
		944	add $grp aio_open "...", sub {
		945	$grp->result ("ok");
		946	};
		947	};
		948
		949	This makes it very easy to create composite requests (see the source of
		950	C<aio_move> for an application) that work and feel like simple requests.
		951
		952	=over 4
		953
		954	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		955	C<IO::AIO::poll_cb>, just like any other request.
		956
		957	=item * They can be canceled like any other request. Canceling will cancel not
		958	only the request itself, but also all requests it contains.
		959
		960	=item * They can also can also be added to other IO::AIO::GRP objects.
		961
		962	=item * You must not add requests to a group from within the group callback (or
		963	any later time).
		964
		965	=back
		966
		967	Their lifetime, simplified, looks like this: when they are empty, they
		968	will finish very quickly. If they contain only requests that are in the
		969	C<done> state, they will also finish. Otherwise they will continue to
		970	exist.
		971
		972	That means after creating a group you have some time to add requests. And
		973	in the callbacks of those requests, you can add further requests to the
		974	group. And only when all those requests have finished will the the group
		975	itself finish.
		976
		977	=over 4
		978
		979	=item add $grp ...
		980
		981	=item $grp->add (...)
		982
		983	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		984	be added, including other groups, as long as you do not create circular
		985	dependencies.
		986
		987	Returns all its arguments.
		988
		989	=item $grp->cancel_subs
		990
		991	Cancel all subrequests and clears any feeder, but not the group request
		992	itself. Useful when you queued a lot of events but got a result early.
		993
		994	=item $grp->result (...)
		995
		996	Set the result value(s) that will be passed to the group callback when all
		997	subrequests have finished and set thre groups errno to the current value
		998	of errno (just like calling C<errno> without an error number). By default,
		999	no argument will be passed and errno is zero.
		1000
		1001	=item $grp->errno ([$errno])
		1002
		1003	Sets the group errno value to C<$errno>, or the current value of errno
		1004	when the argument is missing.
		1005
		1006	Every aio request has an associated errno value that is restored when
		1007	the callback is invoked. This method lets you change this value from its
		1008	default (0).
		1009
		1010	Calling C<result> will also set errno, so make sure you either set C<$!>
		1011	before the call to C<result>, or call c<errno> after it.
		1012
		1013	=item feed $grp $callback->($grp)
		1014
		1015	Sets a feeder/generator on this group: every group can have an attached
		1016	generator that generates requests if idle. The idea behind this is that,
		1017	although you could just queue as many requests as you want in a group,
		1018	this might starve other requests for a potentially long time. For
		1019	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1020	requests, delaying any later requests for a long time.
		1021
		1022	To avoid this, and allow incremental generation of requests, you can
		1023	instead a group and set a feeder on it that generates those requests. The
		1024	feed callback will be called whenever there are few enough (see C<limit>,
		1025	below) requests active in the group itself and is expected to queue more
		1026	requests.
		1027
		1028	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1029	not impose any limits).
		1030
		1031	If the feed does not queue more requests when called, it will be
		1032	automatically removed from the group.
		1033
		1034	If the feed limit is C<0>, it will be set to C<2> automatically.
		1035
		1036	Example:
		1037
		1038	# stat all files in @files, but only ever use four aio requests concurrently:
		1039
		1040	my $grp = aio_group sub { print "finished\n" };
		1041	limit $grp 4;
		1042	feed $grp sub {
		1043	my $file = pop @files
		1044	or return;
		1045
		1046	add $grp aio_stat $file, sub { ... };
		1047	};
		1048
		1049	=item limit $grp $num
		1050
		1051	Sets the feeder limit for the group: The feeder will be called whenever
		1052	the group contains less than this many requests.
		1053
		1054	Setting the limit to C<0> will pause the feeding process.
		1055
		1056	=back
		1057
211	=head2 SUPPORT FUNCTIONS	1058	=head2 SUPPORT FUNCTIONS
		1059
		1060	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
212		1061
213	=over 4	1062	=over 4
214		1063
215	=item $fileno = IO::AIO::poll_fileno	1064	=item $fileno = IO::AIO::poll_fileno
216		1065
…		…
221		1070
222	See C<poll_cb> for an example.	1071	See C<poll_cb> for an example.
223		1072
224	=item IO::AIO::poll_cb	1073	=item IO::AIO::poll_cb
225		1074
226	Process all outstanding events on the result pipe. You have to call this	1075	Process some outstanding events on the result pipe. You have to call this
227	regularly. Returns the number of events processed. Returns immediately	1076	regularly. Returns the number of events processed. Returns immediately
228	when no events are outstanding.	1077	when no events are outstanding. The amount of events processed depends on
		1078	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1079
		1080	If not all requests were processed for whatever reason, the filehandle
		1081	will still be ready when C<poll_cb> returns.
229		1082
230	Example: Install an Event watcher that automatically calls	1083	Example: Install an Event watcher that automatically calls
231	IO::AIO::poll_cb with high priority:	1084	IO::AIO::poll_cb with high priority:
232		1085
233	Event->io (fd => IO::AIO::poll_fileno,	1086	Event->io (fd => IO::AIO::poll_fileno,
234	poll => 'r', async => 1,	1087	poll => 'r', async => 1,
235	cb => \&IO::AIO::poll_cb);	1088	cb => \&IO::AIO::poll_cb);
236		1089
		1090	=item IO::AIO::max_poll_reqs $nreqs
		1091
		1092	=item IO::AIO::max_poll_time $seconds
		1093
		1094	These set the maximum number of requests (default C<0>, meaning infinity)
		1095	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1096	the maximum amount of time (default C<0>, meaning infinity) spent in
		1097	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1098	of time C<poll_cb> is allowed to use).
		1099
		1100	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1101	syscall per request processed, which is not normally a problem unless your
		1102	callbacks are really really fast or your OS is really really slow (I am
		1103	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1104
		1105	Setting these is useful if you want to ensure some level of
		1106	interactiveness when perl is not fast enough to process all requests in
		1107	time.
		1108
		1109	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1110
		1111	Example: Install an Event watcher that automatically calls
		1112	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1113	program get the CPU sometimes even under high AIO load.
		1114
		1115	# try not to spend much more than 0.1s in poll_cb
		1116	IO::AIO::max_poll_time 0.1;
		1117
		1118	# use a low priority so other tasks have priority
		1119	Event->io (fd => IO::AIO::poll_fileno,
		1120	poll => 'r', nice => 1,
		1121	cb => &IO::AIO::poll_cb);
		1122
237	=item IO::AIO::poll_wait	1123	=item IO::AIO::poll_wait
238		1124
		1125	If there are any outstanding requests and none of them in the result
239	Wait till the result filehandle becomes ready for reading (simply does a	1126	phase, wait till the result filehandle becomes ready for reading (simply
240	C<select> on the filehandle. This is useful if you want to synchronously wait	1127	does a C<select> on the filehandle. This is useful if you want to
241	for some requests to finish).	1128	synchronously wait for some requests to finish).
242		1129
243	See C<nreqs> for an example.	1130	See C<nreqs> for an example.
244		1131
		1132	=item IO::AIO::poll
		1133
		1134	Waits until some requests have been handled.
		1135
		1136	Returns the number of requests processed, but is otherwise strictly
		1137	equivalent to:
		1138
		1139	IO::AIO::poll_wait, IO::AIO::poll_cb
		1140
245	=item IO::AIO::nreqs	1141	=item IO::AIO::flush
246		1142
247	Returns the number of requests currently outstanding (i.e. for which their	1143	Wait till all outstanding AIO requests have been handled.
248	callback has not been invoked yet).
249		1144
250	Example: wait till there are no outstanding requests anymore:	1145	Strictly equivalent to:
251		1146
252	IO::AIO::poll_wait, IO::AIO::poll_cb	1147	IO::AIO::poll_wait, IO::AIO::poll_cb
253	while IO::AIO::nreqs;	1148	while IO::AIO::nreqs;
254		1149
		1150	=back
		1151
		1152	=head3 CONTROLLING THE NUMBER OF THREADS
		1153
		1154	=over
		1155
		1156	=item IO::AIO::min_parallel $nthreads
		1157
		1158	Set the minimum number of AIO threads to C<$nthreads>. The current
		1159	default is C<8>, which means eight asynchronous operations can execute
		1160	concurrently at any one time (the number of outstanding requests,
		1161	however, is unlimited).
		1162
		1163	IO::AIO starts threads only on demand, when an AIO request is queued and
		1164	no free thread exists. Please note that queueing up a hundred requests can
		1165	create demand for a hundred threads, even if it turns out that everything
		1166	is in the cache and could have been processed faster by a single thread.
		1167
		1168	It is recommended to keep the number of threads relatively low, as some
		1169	Linux kernel versions will scale negatively with the number of threads
		1170	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1171	versions, 4-32 threads should be fine.
		1172
		1173	Under most circumstances you don't need to call this function, as the
		1174	module selects a default that is suitable for low to moderate load.
		1175
		1176	=item IO::AIO::max_parallel $nthreads
		1177
		1178	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1179	specified number of threads are currently running, this function kills
		1180	them. This function blocks until the limit is reached.
		1181
		1182	While C<$nthreads> are zero, aio requests get queued but not executed
		1183	until the number of threads has been increased again.
		1184
		1185	This module automatically runs C<max_parallel 0> at program end, to ensure
		1186	that all threads are killed and that there are no outstanding requests.
		1187
		1188	Under normal circumstances you don't need to call this function.
		1189
		1190	=item IO::AIO::max_idle $nthreads
		1191
		1192	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1193	threads that did not get a request to process within 10 seconds). That
		1194	means if a thread becomes idle while C<$nthreads> other threads are also
		1195	idle, it will free its resources and exit.
		1196
		1197	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1198	to allow for extremely high load situations, but want to free resources
		1199	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1200
		1201	The default is probably ok in most situations, especially if thread
		1202	creation is fast. If thread creation is very slow on your system you might
		1203	want to use larger values.
		1204
		1205	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1206
		1207	This is a very bad function to use in interactive programs because it
		1208	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1209	use an C<aio_group> together with a feed callback.
		1210
		1211	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1212	do queue up more than this number of requests, the next call to the
		1213	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1214	function will block until the limit is no longer exceeded.
		1215
		1216	The default value is very large, so there is no practical limit on the
		1217	number of outstanding requests.
		1218
		1219	You can still queue as many requests as you want. Therefore,
		1220	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1221	as a stop gap to shield against fatal memory overflow (with large values).
		1222
		1223	=back
		1224
		1225	=head3 STATISTICAL INFORMATION
		1226
		1227	=over
		1228
255	=item IO::AIO::flush	1229	=item IO::AIO::nreqs
256		1230
257	Wait till all outstanding AIO requests have been handled.	1231	Returns the number of requests currently in the ready, execute or pending
		1232	states (i.e. for which their callback has not been invoked yet).
258		1233
259	Strictly equivalent to:	1234	Example: wait till there are no outstanding requests anymore:
260		1235
261	IO::AIO::poll_wait, IO::AIO::poll_cb	1236	IO::AIO::poll_wait, IO::AIO::poll_cb
262	while IO::AIO::nreqs;	1237	while IO::AIO::nreqs;
263		1238
		1239	=item IO::AIO::nready
		1240
		1241	Returns the number of requests currently in the ready state (not yet
		1242	executed).
		1243
264	=item IO::AIO::poll	1244	=item IO::AIO::npending
265		1245
266	Waits until some requests have been handled.	1246	Returns the number of requests currently in the pending state (executed,
267		1247	but not yet processed by poll_cb).
268	Strictly equivalent to:
269
270	IO::AIO::poll_wait, IO::AIO::poll_cb
271	if IO::AIO::nreqs;
272
273	=item IO::AIO::min_parallel $nthreads
274
275	Set the minimum number of AIO threads to C<$nthreads>. The default is
276	C<1>, which means a single asynchronous operation can be done at one time
277	(the number of outstanding operations, however, is unlimited).
278
279	It is recommended to keep the number of threads low, as some Linux
280	kernel versions will scale negatively with the number of threads (higher
281	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
282	threads should be fine.
283
284	Under normal circumstances you don't need to call this function, as this
285	module automatically starts some threads (the exact number might change,
286	and is currently 4).
287
288	=item IO::AIO::max_parallel $nthreads
289
290	Sets the maximum number of AIO threads to C<$nthreads>. If more than
291	the specified number of threads are currently running, kill them. This
292	function blocks until the limit is reached.
293
294	This module automatically runs C<max_parallel 0> at program end, to ensure
295	that all threads are killed and that there are no outstanding requests.
296
297	Under normal circumstances you don't need to call this function.
298
299	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
300
301	Sets the maximum number of outstanding requests to C<$nreqs>. If you
302	try to queue up more than this number of requests, the caller will block until
303	some requests have been handled.
304
305	The default is very large, so normally there is no practical limit. If you
306	queue up many requests in a loop it it often improves speed if you set
307	this to a relatively low number, such as C<100>.
308
309	Under normal circumstances you don't need to call this function.
310		1248
311	=back	1249	=back
312		1250
313	=cut	1251	=cut
314		1252
…		…
318		1256
319	# try to generate nice filehandles	1257	# try to generate nice filehandles
320	my $sym = "IO::AIO::fd#$_[0]";	1258	my $sym = "IO::AIO::fd#$_[0]";
321	local *$sym;	1259	local *$sym;
322		1260
323	open *$sym, "+<&$_[0]" # usually under any unix	1261	open *$sym, "+<&=$_[0]" # usually works under any unix
324	or open *$sym, "<&$_[0]" # cygwin needs this	1262	or open *$sym, "<&=$_[0]" # cygwin needs this
325	or open *$sym, ">&$_[0]" # cygwin needs this	1263	or open *$sym, ">&=$_[0]" # or this
326	or return undef;	1264	or return undef;
327		1265
328	*$sym	1266	*$sym
329	}	1267	}
330		1268
331	min_parallel 4;	1269	min_parallel 8;
332		1270
333	END {	1271	END { flush }
334	max_parallel 0;
335	}
336		1272
337	1;	1273	1;
338		1274
		1275	=head2 FORK BEHAVIOUR
		1276
		1277	This module should do "the right thing" when the process using it forks:
		1278
		1279	Before the fork, IO::AIO enters a quiescent state where no requests
		1280	can be added in other threads and no results will be processed. After
		1281	the fork the parent simply leaves the quiescent state and continues
		1282	request/result processing, while the child frees the request/result queue
		1283	(so that the requests started before the fork will only be handled in the
		1284	parent). Threads will be started on demand until the limit set in the
		1285	parent process has been reached again.
		1286
		1287	In short: the parent will, after a short pause, continue as if fork had
		1288	not been called, while the child will act as if IO::AIO has not been used
		1289	yet.
		1290
		1291	=head2 MEMORY USAGE
		1292
		1293	Per-request usage:
		1294
		1295	Each aio request uses - depending on your architecture - around 100-200
		1296	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1297	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1298	scalars and other data passed into aio requests will also be locked and
		1299	will consume memory till the request has entered the done state.
		1300
		1301	This is not awfully much, so queuing lots of requests is not usually a
		1302	problem.
		1303
		1304	Per-thread usage:
		1305
		1306	In the execution phase, some aio requests require more memory for
		1307	temporary buffers, and each thread requires a stack and other data
		1308	structures (usually around 16k-128k, depending on the OS).
		1309
		1310	=head1 KNOWN BUGS
		1311
		1312	Known bugs will be fixed in the next release.
		1313
339	=head1 SEE ALSO	1314	=head1 SEE ALSO
340		1315
341	L<Coro>, L<Linux::AIO>.	1316	L<Coro::AIO>.
342		1317
343	=head1 AUTHOR	1318	=head1 AUTHOR
344		1319
345	Marc Lehmann <schmorp@schmorp.de>	1320	Marc Lehmann <schmorp@schmorp.de>
346	http://home.schmorp.de/	1321	http://home.schmorp.de/

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